LOVED the movie, BUT...

Personally, (but hey, who am I,) I interpreted it as the following:

-Palantine was in Travis' cab earlier in the film, and although he expressed sympathy towards Travis because he is of course a potential voter, Palantine seemed disturbed by Travis' ideas. (Debatable is however if Travis noticed this.)

-Betsy was very fond of Palantine and his ideas, and after she refused Travis he even came to the "Palantine headquarters" to confront her. But he quickly left as Betsy's coworkers threatened to call the police. This particular occasion and Betsy's refusal of Travis and obsession with Palantine was probably a lot of reason for Travis to start to hate Palantine.

-Travis often spoke of wanted to do "something big". Whatever this was, especially when he began to became to be dangerously unstable this was probably something violent. And murdering a big icon of society would gain him a lot of attention. Even though it would mean his own death. Keep in mind that Travis didn't know a lot of famous people. He didn't know any mainstream movies, didn't know anything about music and was not interested in politics.

I think this is what made him target Palantine. But of course he was far too wel protected and Travis' plan failed in an early stage. Turning Travis to the only other logical target: Matthew 'Sport'.


Go make a movie!

Because he was a bad tipper.

Travis was not trying to impress Betsy. He was trying to get revenge on her by taking away the thing that she cared about. She took herself away from Travis, so he was going to take away Palantine from her.

Travis's plan was to kill Palantine to get even with Betsy, then kill Sport to free Iris, and then kill himself. He didn't expect to be around at the end of it.

In most movies the protagonist is not insane, audiences are not used to dealing with getting to know such a character. We tend to try to sympathize with him/her, then when s/he does something clearly unacceptable we wonder. The reason Travis decides that his purpose in life is to assassinate Pallantine is basically that Bickle is insane. By this time in the movie we've come to accept Travis as a person, so we are taken aback, we experience a paradigm shift which reinforces a diabolical direction already undertaken in the movie which we only now realize is as bad as it is. Travis is clueless to the fact that he has chosen Pallantine because of Betsy's rejection of Travis. Travis is delusional, imagining himself someone he is not, someone on a kind of righteous mission. He doesn't realize that his plans are not good but evil. He cannot tell right from wrong; in other words, he's crazy.